1. Field of the Invention
The invention relates to a separating body which can be set into rotation for the purpose of separating solid or liquid particles of micron or sub-micron sire from a fluid, wherein the relevant body consists of a large number of separating ducts with singly connected walls over a substantial part of the axial length. The invention also relates to a rotating particle separator which consists of the above described separating body, onto which impellers may or may not be fixed upstream and downstream and wherein the separating body is mounted in a housing which is provided with a fluid inlet and fluid outlet, optionally with a separate outlet for removing separated particle material.
2. Description of the Prior Art
When a fluid is set into rotation, liquid or solid particles found in the relevant fluid will displace in a radial direction, wherein the distance of the particles from the axis of rotation increases. The velocity with which the particles are displaced in a radial direction depends on the magnitude of the centrifugal force acting on the particle as a result of the rotation and the resistant force the fluid exerts on a particle making a movement relative to the fluid. On the basis of these forces it can be calculated that in the case of a gas rotating at an angular speed of 300 rad/s a particle with an average diameter of 1 micron, an average specific mass of about 1000 kg/m.sup.3 and situated on a radius of 0.1 m, displaces radially at a speed of about 0.03 m/s. Particles with average diameters of about 5 micron and about 0.05 micron will as a result of rotation generally be displaced radially, under practically realistic conditions, at respective speeds of about 0.1 m/s and about 0.001 m/s. If we assume that gas and particles remain in rotation for a residence time of about 0.2 s, this then implies that the said particles will arrive at a radially placed wall if the said wall is situated at a radial distance which is respectively about 20 mm and about 0.2 mm removed from the radial plane where the particles start their displacement. The use of a large number of walls placed at a short radial distance from each other and extending axially along the axis of rotation results in a configuration with which large amounts of gas can be purified of extremely small particles by means of centrifugal separation. The gas moves parallel to the radially placed walls and the axis of rotation, while the particles displace radially as a result of centrifugal action and are deposited on the outer walls of the separating ducts which are formed by the radially placed walls. Similar considerations also apply for a liquid fluid.
The above specified particle separator is known from the European patent specification 0286160 and the U.S. Pat. Nos. 4,994,097 and 5,073,177. A drawback of the known particle separator is that the separating ducts are parallel to the axis of rotation. The present invention is based on the new insight that within defined limits the separating ducts are placed non-parallel to the axis of rotation, which positively enhances the separating process.